Oscillating free piston pump



Jan. 13, 1970 M. SCHUMAN\ 3,489,335

OSCILLATING FREE PISTON PUMP Filed July 31, 1968 2 Sheets-Sheet l E 3 LJ K (0 W4 Q14 rm m W E 2/ 19 FIGS INVENTOR MARK SCH UMAN wa /Ei- BY q/gw fiwmf/ g M ATTORNEYS Jan. 13, 1970 M. SCHUMAN 3,489,335

OSOILLATING FREE PISTON PUMP Filed July 31, 1968 2 Sheets-Sheet 2 57FIG. IO

WARM fiesmvo/ FIG. [2

ii I INVENTOR MARK SCHUMAN BY gwfl M ATTORNEYS United States Patent O3,489,335 OSCILLATING FREE PISTON PUMP Mark Schuman, Ann Arbor, Mich.(101 G St. SW., A516, Washington, D.C. 20024) Filed July 31, 1968, Ser.No. 749,130 Int. Cl. F04b 35/00 U.S. Cl. 230-51 6 Claims ABSTRACT OF THEDISCLOSURE A thermal powered pump formed of a cylinder, containing afree, oscillating piston, and having a heating chamber for providingabove the piston, heated, expanding gases to be pumped for moving thepiston downwardly to compress the gas located beneath it which, in turnraises piston so that the piston oscillates up and down, and with thepump outlet located above the piston for expelling the gas. A shuntinterconnects the cylinder portions above and below the piston forcarrying gas to the portion below the piston for maintaining the centerof oscillation of the piston with respect to the cylinder.

BACKGROUND OF INVENTION Conventional piston type pumps used for pumpinggases, such as air or the like, generally include a cylinder containinga movable piston which is connected to a motor or engine as a poweroperating means for the pump. In addition, such types of pumps aregenerally bulky, noisy, and relatively expensive in construction, andcannot operate on continuously applied thermal power.

Thus, this invention is concerned with providing a simply construction,thermally powered pump mechanism, in the form of a free floating pistonoscillating within a cylinder. Power is supplied by a suitable heatingmeans, such as a continuously operated electrical heating coil orcarbon-type fuel heater, which is relatively eflicient and inexpensive.The relative size of the pump, as compared to prior pumps, is reducedand its noise of operation, both electrical and audible, is considerablyreduced. The improved pump may serve a number of pumping functions, asfor example, to provide high pressure gases to a turbine orturbo-generator, etc.

SUMMARY OF INVENTION Summarizing, the invention herein contemplatesoscillating a free piston by means of initially placing it between equalvolumes of gas which act like a pair of compression springs to push thepiston back and forth between them, but with one spring having an addedpush on its expansion to prevent the oscillation from dying out. Thus,one of the gas volumes is heated and expands to push the piston tocompress the other gas volume which rebounds like a spring to return thepiston to expel, and

thereby pump the heated gas. The repeated oscillation steps generallycomprise supplying heated expanding gas, movement of piston to compressthe opposite gas volume, and rebound and expulsion of the heated gas.The supply of heated gas provides the pressure to maintain theoscillation and prevent it from slowing down and stopping. Additionalgas is intermittently supplied to the opposite gas volume to maintainthe center of oscillation of the piston. The oscillation is initiallystarted by use of an auxiliary starting pump which use is discontinuedonce the piston oscillation stabilizes.

An object of this invention is to drive an oscillating, free pistonwithin a cylinder by means of heated expanding gas applied to one faceof the piston and non-heated compressed gas, which is compressed by thepiston itself, at the opposite face of the piston, and to expel or pumpthe heated gas.

Patented Jan. 13, 1970 f ce Another object is to provide a simple, quietoperating pump construction utilizing a constantly operated heater whichcontinually, rather than intermittently, heats he gas, but wherein thegas intermittently applies pressure to the piston to cause continuedoscillation thereof.

Another object of this invention is to utilize, as the ther mal powermeans for such pump, a temperature differ ential provided by means ofheating and cooling reservoirs, or by means of natural temperaturedifierentials such as the heat of sunlight as compared to ambienttemperature or available water temperature or the like.

A further object of this invention is to provide a pump as describedabove but utilizing a double action operation, which includes a pair ofopposed pistons operating oppositely and synchronously to therebybalance out low frequency piston vibrations.

These and other objects and advantages of this inven tion will becomeapparent, upon reading the following description, of which the attacheddrawings form a part.

DESCRIPTION OF DRAWINGS FIG. 1 is a schematic, elevational,cross-sectional view of the oscillating free piston pump herein.

FIG. 2 is an enlarged, cross-sectional schematic view of the upper,heating chamber portion of the cylinder.

FIG. 3 is an enlarged, fragmentary, elevational view of the piston and aportion of the cylinder.

FIGS. 4 through 8 show successive steps in the operation of the pump.

FIG. 9 schematically illustrates the use of the pump in powering aturbo-generator, and also illustrates a modified heater.

FIG. 10 illustrates a modification wherein a heat diiferential isutilized to provide the thermal power.

FIG. 11 illustrates a further modification showing a double acting pumputilizing a pair of opposed free pistons.

FIG. 12 illustrates another modification similar to that of FIG. 10.

DETAILED DESCRIPTION FIG. 1 illustrates a pump 10 formed of a verticallyarranged, closed cylinder 11, containing a loosely fitted, free piston12 adapted to oscillate vertically up and down within the cylinder. Thecylinder includes an inlet pipe 13 through which the gas to be pumpedenters the cylinder.

Between the inlet pipe and the body of the cylinder is arranged aheating chamber 14 containing a suitable heating element 15 such as anelectrical heating coil powered by an outside electrical source, such asa conventional house circuit.

The inlet to the heating chamber is closed by a valve 16 and the outletis closed by a valve 17, these being one- Way type of valves, passingthe gas only in the direction from the inlet towards the main body ofthe cylinder and closing when necessary to prevent the gas fromreturning back to the inlet.

A pump outlet pipe 18 is arranged at the upper portion of the cylinderand contains a suitable one-way outlet valve, as for example, aconventional ball check valve 19, which leads into a surge or storagetank 20' for smoothing out the pulsating pumped gas.

A shunt pipe 21 is arranged around the cylinder, with its upper end 22connected to the inlet pipe 13 and its lower end 23 connected to theinterior of the bottom of the cylinder through a one-way inlet valve 24,such as a suitable ball check valve or the like which permits the flowof gas into the bottom of the cylinder through the shunt pipe but not inthe reverse direction.

The piston 12, being loosely fitted within the cylinder, is gaslubricated for substantially frictionless movement. Preferably, thepiston is formed of a cylindrically shaped,

porous, sintered metal, side wall 25 which is gas pervious (see FIG. 3).The piston is closed by a top cover 26 having a central opening 27 andclosed by a suitable oneway valve 28 (shown schematically) so that itwill fill with gas on its up stroke while permitting the pressurized gasto continuously leak through the wall 25. This serves to gas lubricatethe piston relative to the cylinder wall and to maintain the pistonco-axially with the cylinder.

While a variety of one-way valves may be found for the inlet and outletof the heating chamber, FIG. 2 illustrates one suitable form whichcomprises wafers 16 and 17 having an inlet stop or limit 29 and anoutlet stop or limit 31. The outlet stop provides a greater distance ofmovement for the wafer 17 than is provided for the wafer 16 so that thewafer 17, in efiect, is a delayed acting valve because of its greaterrequired movement and lower restriction of reverse gas flow. The wafersclose the inlet opening 30 and the outlet opening 32 of the heatingchamber 14. The object here is to provide an outlet valve for theheating chamber which closes at a short time interval after the inletvalve closes for reasons to be explained below. Thus, other forms ofvalves such as solenoid operated valves or other suitable timed valvesmay be utilized for this purpose.

Referring to FIG. 1, the pump also includes an auxiliary starter pump 35for start-up purposes. This comprises an inlet pipe 36 leading from thebottom of the cylinder and opening into a bellows 37 which is connectedto a piston rod 38 having a piston 39 arranged within a cylinder 40containing a compression spring 41. In addition, the rod is surroundedby a conventional solenoid coil 42. The solenoid is arranged toperiodically move the piston rod 38 to the left, as referring to FIG. 1,whereas the spring -41 returns the piston rod to the right to therebypump the bellows. The bellows sucks gas out of the cylinder to lower thepiston 12, and pumps gas into the cylinder to raise the piston 12. It isused for a short time to start the normal pump operation.

OPERATION During normal operation, the piston oscillates upwardly anddownwardly, with heated gas entering the cylinder, above the piston,from the heating chamber and with this gas being pumped out of thecylinder through the outlet 18 during the top portion upstroke of thepiston stroke. FIGS. 4 through 8 schematically show certain of the stepsin the operation of the pump.

FIG. 4 illustrates the piston travelling upwardly near the top of itsupstroke. Here the heating chamber valves 16 and 17 are closed, gas isbeing expelled through the outlet 18 whose check valve 19 is open. Thearrows beneath the piston, within the cylinder, represent the expansionor rebound of gas, located below the piston, which has been previouslycompressed by the downward movement of the piston.

During this time, the heating element 15, which is continuouslyoperated, heats the gas contained within the heating chamber 14, causingthe gas pressure to increase, as shown by the arrows in FIG. 4. Next, asseen in FIG. 5, gas compressed by the upward movement of the piston,slows such upward movement, stops it, and starts to drive it downwardly.Simultaneously, gas exhausts through outlet 18, until outlet check valve19 closes due to the higher pressure of the gas contained within thesurge tank 20. In FIG. 5, the valve 16 is shown in its open position.

In addition, a small amount of gas, as needed, may enter into the bottomof the cylinder through the shunt pipe 21, whose check valve 24 is openso that pressure below the piston does not drop below the inletpressure. Where the gas being pumped is atmospheric air, the shunt pipemay be omitted and the check valve simply opened to atmosphere, so that,in efiect, there is still a shunt.

In FIG. 6, the exhaust check valve 19 is closed, and the pressure of thegas in the heating chamber 14 causes inlet valve 17 to open to releaseheated gas into the cylinder, which gas expands and drives the pistondown.

As the piston moves further down, reducing the pressure within theheating chamber to below inlet 13 pressure, the heating chamber inletvalve 16 also opens to admit more gas through the inlet 13 (see FIG. 7).The downward movement of the piston not only permits the cylinderportion above the piston to become filled with the incoming gas, butalso compresses the gas located Within the cylinder below the piston.Hence, at the lowermost part of the stroke downwardly, the compressedgas beneath the piston reaches its point of maximum compression where itand the piston tend to rebound as a result of this pressure exceedingthe pressure above the piston. At that point, as shown in FIG. 8, thepiston again starts upwardly, compressing the gas above it, andexpelling a portion of the gas into the heating chamber 14 through thevalve 17 which remains open slightly longer than does the upper valve 16to insure closing of the valve 1 6 and to accumulate additional gaswithin the heating chamber for higher efficiency. As the piston risestowards the top of the stroke, the pressure above it exceeds the surgetank pressure and gas is expelled out the outlet 18. The cycle is thenrepeated as shown beginning with FIG. 4.

In this manner, the piston rapidly oscillates upwardly and downwardly,pumping out a pulsating discharge into the surge tank 20 and relyingupon the continuously applied heat energy to provide it with theexpanding gases necessary for operation.

Before the piston stabilizes and oscillates as described above, at theoutset of its operation, it is necessary to start at the regularoscillation by means of starter 35. In essence, its bellows 37alternately pumps and draws an amount of gas into and from the cylinder,beneath the piston, at approximately the natural frequency of theoscillation of the piston. Thus, the solenoid is properly timed to movethe rod 38 with the bellows at such frequency. The starter is used untilsuch time as the piston oscillation stabilizes, at which time thestarter is turned off. This may amount to a few minutes of operation.

MODIFICATION FIG. 9

FIG. 9 illustrates a modification wherein the heating coil is in theform of a pipe 45 opening into a suitable fossil type heater 46, such asa natural gas burner type heater, connected in turn to a tank 47 of fuelgas. Other types of suitable heaters may be used, such as a petroleumheater, coal burner or the like. The heated gas from the heater 46passes through the coil 45 and then out through the end 48 into adischarge stack.

FIG. 9 also illustrates the pump as being used to power a conventionalturbo-generator 49 which generates electricity. The gas pumped throughthe generator 49 is cooled in a cooling tank 50 or by other coolingmeans such as fins surrounding the return pipe 51 which returns the gasback to the inlet 13. This illustrates a closed circuit gas movementwherein the gas is recirculated.

In the embodiment illustrated in FIG. 1, the gas may be air, in whichcase no recirculation is contemplated, or it may be a gas of more valuewhich required recirculation and hence, interconnection between theinlet and outlet pipes ultimately.

The operation of the pump shown in FIG. 9 is otherwise the same as thatdescribed above.

FIG. 10

FIG. 10 illustrates a further modification which contemplates utilizinga temperature differential in providing the heat to the pump. As anexample, above the heating chamber 14 is located a cooling chamber 55having a cooling coil 56 for first cooling the inlet gases, which arethen heated by the heating coil located within the heating chamber. Oncethe gas is heated and enters the cylinder, the operation is the same asdescribed above, with the gas powering a turbo-generator 49 and thenbeing recirculated back to the cylinder through the return pipe 51.

The coil 56 may be cooled by the use of a cold water reservoir 57, withthe heated coil 58 warmed by a warm reservoir. The cooled reservoir maybe an available water supply, such as a natural well, pond, etc.

It is contemplated that this arrangement may utilize ambienttemperatures and sun heat to operate around the clock. To this end, aheat exchanger coil 60 is provided and mounted upon a panel 61 whichcould be arranged upon a rooftop or out of doors where it is exposed tothe sun. The coil is connected through valve 62 to a cool reservoirinlet pipe 64 and a warm reservoir inlet pipe 65 and through a valve 63to a cool reservoir outlet pipe 66 and a warm reservoir outlet pipe 67.In this case, the reservoirs may be large water tanks. Thus, during theday, when the sun is available to provide heat, by adjusting the valves62 and 63, the liquid in the warm reservoir may be heated and the liquidin the cool reservoir simply left at ambient temperature, preferably ina cool, shaded place. In the evening, when the sun is no longeravailable, the valve 62 and 63 may be reversed to utilize radiantcooling and the cold ambient temperature to cool the cool reservoirfurther below the liquid in the warm reservoir.

In this manner, the net result is that the gas entering through inlet 13is first cooled by the coil 56 and is then heated by the coil 58 toprovide for greater pressure buildup and subsequent expansion. Thus, thedifferential of temperature, provided as described above or in otherequivalent ways, serves as a means for operating the pump.

FIG. 11

FIG. 11 illustrates a modification in the form of a double ended ordouble acting pump 70 comprising a cylinder 71 containing a pair of freepistons 72 and 73. The inlet 74 delivers the gas to the heating chamber75 which contains the heating coil 76 and has an inlet valve 77 and anoutlet valve 78 located between the two pistons. Also, the pump outletpipe 79 is located between the two pistons and discharges through aone-way valve 80 into the surge tank 81.

The opposite ends of the cylinder are connected to the inlet 74 by meansof a shunt pipe 82 containing one-way valves 83 at each end of thecylinder.

For purposes of starting the pump, a pair of starters 35 are provided ateach end of the cylinder, although one starter might be used with pipesleading to each of the opposite ends.

The operation of this pump is the same as described before except here,the two pistons move oppositely and synchronously.

FIG. 12

FIG. 12 illustrates a modification similar to that of FIG. 10, with theexception that no separate heating chamber is provided below coolingchamber 55 which contains the cooling coil 56 and is closed at itsbottom by a one-way valve 85. Here the heating coil is exposed above thepiston. While heating the gas in the up-stroke is relativelyinefi'icient, this construction is simpler and may have certain lowefficiency applications.

Having fully described an operative embodiment of this invention, I nowclaim:

1. An oscillating free piston pump, for pumping gas, comprising a closedvertical cylinder containing a free piston loosely fitted therein forvertical oscillation;

a gas inlet and a gas outlet located above the piston, the

inlet being also connected by a shunt pipe through a shunt one-way valveto the opposite end of the cylinder for permitting gas to flow into thecylinder below the piston;

a heating chamber connected between said inlet and the cylinder abovethe piston for heating incoming gas before entry into the cylinder andhaving a oneway chamber inlet and chamber outlet valves for controllinggas flow only towards the cylinder and for closing upon upward movementof the piston, with the chamber outlet valve being formed to closeshortly after the chamber inlet valve closes;

said gas outlet having a one-way outlet valve for passing the pumped gasonly out of the cylinder;

whereby downward movement of the piston is efiected by expansion of theheated gases entering the cylinder from the heating chamber and by gascompressed above the piston applying a force to the top of the piston,and upwards movement of the piston is effected solely by compression andrebound of the compressed gas below the piston applying an upwards forceupon the bottom of the piston.

2. A construction as defined in claim 1, and including a starter pumpconnected to the cylinder below the piston, said starter pump havingmeans for regularly and periodically pumping gas into and out of thecylinder below the piston at the natural frequency of oscillation of thepiston for a period of time sufficient to stabilize the normaloscillation of the piston within the cylinder.

3. A construction as defined in claim 1, and including a heater elementcontained within said heater chamber and constantly operated to maintaina continuous heat input into said chamber by an outside source of heatenergy.

4. A construction as defined in claim 1, and including a coolingchamber, containing means for cooling gases passed therethrough,connected between the gas inlet and heating chamber for reducing thetemperature of and contracting the specific volume of the gas prior toentry of the inlet gas into said heating chamber.

5. A construction as defined in claim 1, and including a second freepiston located in the cylinder spaced above the first piston and the gasinlet and outlet, with the upper end of the cylinder also connected tothe gas inlet by a shunt pipe containing a one-way shunt valve forcontrolling gas flow only into the upper end of the piston above thesecond piston;

whereby the two pistons move respectively oppositely and synchronouslyupon entry of heated gas into the cylinder between them and upon reboundof the compressed gas when the pistons reach near their respectiveopposite cylinder ends.

6. An oscillating free piston pump for pumping a gas, comprising aclosed cylinder containing a free piston loosely fitted therein foroscillation along the axis of the cylinder;

said piston dividing the cylinder into a pumping chamber closed by anend of the piston and compression chamber closed by the opposite end ofthe piston;

a gas inlet and a gas outlet located in said pumping chamber with acontinuously operating heater located between said inlet and outlet, andincluding a one-way inlet valve at said inlet and a one-way exit valveat said outlet;

means for initially starting the piston to oscillate within said chamberat a predetermined frequency;

and means for connecting the compression chamber to inlet gas pressureat about the time that the piston reaches the end of its stroke towardsthe inlet;

wherein movement by the piston away from the inlet compresses gascontained in the compression chamber until maximum compression isreached and the compressed gas rebounds and acts as the sole means fordriving the piston towards the inlet for expelling gas out through theoutlet and simultaneoutly compressing gas in the pumping chamber, andmovement away from the inlet is efiected by a combination of expandingheated gas entering the pumping chamber and compressed gas resultingfrom piston movement towards the inlet.

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2,910,119 10/1959 wennelbergi WILLIAM L. FREEH, Pnmary Exammer 2,040,4335/ 193 6 Dufiaud.

5 US. Cl. X.R. 3,087,438 4/1963 Ciesielski. 23056

